1. Field of the Invention
This invention relates to a jar for providing high impact loading in a well and a method of operating same, and, more particularly, to such a jar and method in which the loading can be in both an upward and downward direction.
In various downhole operations in wells for producing hydrocarbon fluids, high impact loading is often necessary to retrieve or set tools for servicing the wells. Both mechanical and hydraulic jars have evolved which are lowered into the wellbore in a well tool string including an accelerator and a stem, which together function to produce a high impact load. In the case of an up jar, the load is directed upwardly to retrieve tools, remove obstructions and the like. In the case of a down jar the load is directed downwardly to set tools, plugs, flow control devices, and the like.
The need for efficient jars becomes more acute in wells that deviate from the traditional vertical orientation, since the angular disposition of at least a portion of the well increases the friction in the well and dissipates some of the vertical thrust needed to activate the jars. Further, the advent of coil, or reeled, tubing, which requires a jar that passes fluid used to service the well, places additional design limitations on the up and down jars, especially from a size standpoint.
In view of these structural and functional demands, a separate jar has to be designed and used for the up operation and a separate jar for the down operation, thus adding to the overall cost of the well service tools. The jars disclosed in U.S. Pat. Nos. 2,828,822 and 2,851,110, issued to C.B. Greer on Apr. 1, 1958, and Sep. 9, 1958, respect are exemplary of hydraulic jars that can only operate in an upward direction. Thus an entirely different jar would have to be designed for use in a downward direction.